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Transferable Enzyme-Polymer Stickers for Modular Assembly of Single and Multi-analyte Biosensors
(2026)
Electrochemical biosensors have achieved widespread commercial success due to their high selectivity, ease of use, and low cost. However, the fabrication of many such systems, especially when targeting multianalyte sensing, is often constrained by the preparation of the sensing 5 film, which typically relies on drop-casting polymer–enzyme solutions followed by drying to form the active layer. Depending on the 6 enzyme-polymer formulation, this step can be difficult to integrate into large-scale, roll-to-roll production processes and lacks flexibility for constructing multianalyte sensors. Here, we introduce a new assembly strategy in which sensing films composed of redox-active polymers and enzymes are pre-fabricated as sensor stickers that can be transferred in a single step either onto individual electrodes to generate single-analyte sensors or combined on electrode arrays for multianalyte sensing. We demonstrate the sensor sticker conc ept using four oxidoreductases as biorecognition elements targeting four analytes: hydrogen, formate, nitrate, and NADPH. Accurate sensing was achieved both on conventional glassy carbon electrodes and on custom-designed microelectrode arrays modified with the sensor stickers. The resulting sensors displayed high selectivity with minimal cross-interference, even in complex mixtures containing all four analytes. This modular approach to assembling multianalyte sensors on microarrays is broadly applicable to other analytes and holds strong promise for flexible, customizable, and scalable fabrication of multianalyte biosensors.
Additively processed materials are increasingly used to manufacture customized parts, e.g. medical implants. Implant surfaces often require a smooth finish, which can be achieved by post-processing and well-defined process parameters. In this study, the effects of electropolishing of metal parts produced by laser powder bed fusion are investigated using Hull cell experiments and a three-electrode setup. Current density voltage curves were measured with the three-electrode setup to identify the regimes for electropolishing. Subsequently different constant-currents were applied and Hull cell experiments were conducted. The surface roughness (Sz, Sa) and the mass removal were analysed. Surface morphologies were assessed using laser scanning and scanning electron microscopy. A reduction of the initial surface roughness of more than 90% to Sa < 0.3 μm has been achieved. Considering the passed electrical charge during electropolishing, results from Hull cell experiments are systematically correlated with current-controlled electropolishing. This approach enables the precise tailoring of polishing parameters to achieve surfaces with defined roughness. Furthermore, the study demonstrates the suitability of Hull cells in determining electropolishing parameters for additive materials and highlights their contribution to post-processing in additive manufacturing.
Titan und seine Legierungen finden aufgrund ihrer geringen Oberflächenhärte vorwiegend in wenig verschleißbeanspruchten Bereichen Anwendung. Zur Erhöhung der Härte werden oft Verschleißschutzschichten durch chemische oder physikalische Gasphasenabscheidung eingesetzt. Diese Schichten weisen jedoch mitunter eine schlechte Haftung auf, was zu vorzeitigem Versagen führen kann. Eine Alternative bietet das Diffusionsschweißen, bei dem durch den Konzentrationsgradienten verschiedener Elemente eine Diffusionsschicht zwischen Titan und einem Fügepartner entsteht. Bei hochkohlenstoffhaltigen Stählen bildet sich an der Grenzfläche eine TiC-Schicht. Durch chemisches Auflösen des Stahls kann diese Schicht freigelegt und genutzt werden. Jedoch ist dieses Verfahren noch nicht gänzlich untersucht. Verschiedene Veröffentlichungen treffen widersprüchliche Aussagen, ob neben TiC auch Eisen-Titan-Verbindungen (FeTi oder Fe2Ti) entstehen. Neben der Zusammensetzung ist auch die Mikrostruktur der entstehenden Schicht nicht abschließend untersucht. Ziel dieser Arbeit ist es, das Schichtwachstum anhand thermodynamischer Gesetzmäßigkeiten zu untersuchen. Dabei werden der Einfluss von Temperatur, Zeit und Kohlenstoffkonzentration auf das Diffusionsverhalten und die Schichtbildungsgeschwindigkeit analysiert. Besonders relevant ist, dass der Kohlenstoff in interstitieller Form vorliegt. Die Schichtbildungskinetik wird bildgebend untersucht. Die chemische Zusammensetzung wird mittels Glimmentladungsspektroskopie (GDOES) und energiedispersiver Röntgenspektroskopie (EDS) bestimmt, während die Phasenanalyse durch Röntgendiffraktometrie (XRD) erfolgt. Zur Charakterisierung der Mikrostruktur werden EBSD-Messungen herangezogen. Nanoindentation dient der Ermittlung mechanischer Kennwerte wie E-Modul und Härte. Die Ergebnisse zeigen, dass der Kohlenstoffgehalt des Stahls die Schichtbildung wesentlich beeinflusst. Ein hoher Kohlenstoffanteil kann die Bildung intermetallischer Fe-Ti-Verbindungen unterdrücken. Die mikrostrukturellen Eigenschaften können hingegen nur durch die Prozessparameter (Temperatur und Zeit) beeinflusst werden. Die mechanischen Kennwerte sind nur durch die Phasenzusammensetzung der Schicht, welche in großen Teilen konstant ist, bestimmt. Durch das chemische Entfernen des Stahlsubstrats aus dem Verbund und dem damit einhergehenden Freilegen der Schicht, stellt das Verfahren des Diffusionsschweißens eine alternative Möglichkeit der Beschichtung von Titanbasiswerkstoffen dar. Die vorliegenden Untersuchungen belegen, dass der Prozess bestimmten Grenzen unterliegt, dieser jedoch innerhalb des erarbeiteten Prozessfensters beherrschbar ist. Dies ist der Grund, weshalb dem Diffusionsschweißen großes Potenzial im Bereich der Beschichtungstechnik zuzuordnen ist.
Laser Powder Bed Fusion (L-PBF) parts combine geometric freedom with process-induced rough surfaces that challenge residual-stress metrology. We evaluated the accuracy of the incremental hole-drilling (IHD) method with electronic speckle pattern interferometry (ESPI) by applying defined stresses via four-point bending to stress-relieved AlSi10Mg coupons, rather than measuring unknown process stresses. Flat specimens (2 mm, thin per ASTM E837) were analyzed on up-skin, side-skin, and CNC-milled surfaces; thin-specimen calibration coefficients were used. After a preliminary inter-specimen check (three specimens per surface; spread < 8 MPa), one representative specimen per surface was tested with three drill sites to assess intra-specimen uniformity. Measured IHD–ESPI stresses agreed best at 70 MPa: deviations were ~4.1% (up-skin), 6.0% (side-skin), and 6.24% (CNC-milled). At 10 MPa the relative errors increased (23.6%, 18.4%, and 1.40%), consistent with reduced ESPI signal-to-noise and fixture compliance in the low-stress regime. At 140 MPa, deviations rose again (21.1%, 14.3%, and 13.1%), reflecting operation near the ~60% Rp0.2 elastic limit of hole-drilling and potential local plasticity. Surface-dependent artifacts also mattered as follows: the side-skin required no coating and performed comparably to CNC-milled, whereas the up-skin’s roughness plus matting spray introduced fringe distortions and chip/coating debris near the hole. This controlled study indicates that IHD–ESPI can provide reliable results on L-PBF AlSi10Mg in the mid-stress range when surface preparation, coating, and rig compliance are carefully managed. Limitations include excluding down-skin surfaces and testing only one specimen per condition; thus, results should be generalized cautiously.
Material extrusion is a widely used AM process and is gaining more acceptance in industry applications due to its material variety, flexibility, and low cost. However, its usage is limited by a process-related anisotropy caused by insufficient interlayer bonding due to reduced temperature in the process zone. To enhance layer adhesion, an adaptive laser preheating system is integrated in a conventional printhead around the extrusion nozzle. The setup with eight fiber coupled diode laser allows preheating in feed direction and investigation of various intensity profiles. The article describes the experimental setup and significant improvements achieved. Laser preheating with different intensity distributions (spot, sickle or ring shaped) show an incasement of up to 85 % of the mechanical properties in the build-up direction. However, due to the additional energy input by the laser, controlled cooling of the workpiece becomes a crucial factor and is investigated as well.
Absorber-free laser transmission welding is characterized by its contactless energy input and geometricflexibility and enables the precise and clean joining of polymer films without absorbing additives or adhesives. It is therefore well suited for applications with high demands regarding process reliability and cleanliness such as packaging, fluid containersor as sealing film in medicaland food industry. A homogeneous weld seam temperature is necessary for a large processwindow. In this work, the naturally Gaussian-shaped intensity distributionof the laser beam is there foreconverted into a donut-shaped and a flat-top-shaped distribution. When using the donut-shape, the processwindow for welding polypropylene or polyethylene films is increased by up to a factor of 3. At the same time, the weld seam strength almost corresponds to the strength of the base material.
Fused filament fabrication (FFF) is a widely used additive manufacturing process for producing functional components and prototypes. The FFF process involves depositing melted material layer-by-layer to build up 3D physical parts. The quality of the final product depends on several factors, including the component density and tensile strength, which are typically determined through destructive testing methods. X-ray microtomography (XCT) can be used to investigate the pore sizes and distribution. These approaches are time-consuming, costly, and wasteful, making it unsuitable for high-volume manufacturing. In this paper, a new method for non-destructive determination of component density and estimation of the tensile strength in FFF processes is proposed. This method involves the use of gradual error detection by sensors and convolutional neural networks. To validate this approach, a series of experiments has been conducted. Component density and tensile strength of the printed specimens with varying extrusion factor were measured using traditional destructive testing methods and XCT. The cumulative error detection method was used to predict the same properties without destroying the specimens. The predicted values were then compared with the measured values, and it was observed that the method accurately predicted the component density and tensile strength of the tested parts. This approach has several advantages over traditional destructive testing methods. The method is faster, cheaper, and more environmentally friendly since it does not require the destruction of the product. Moreover, it facilitates the testing of each individual part instead of assuming the same properties for components from one series. Additionally, it can provide real-time feedback on the quality of the product during the manufacturing process, allowing for adjustments to be made as needed. The advancement of this approach points toward a future trend in non-destructive testing methodologies, potentially revolutionizing quality assurance processes not only for consumer goods but various industries such as electronics or automotive industry. Moreover, its broader applications extend beyond FFF to encompass other additive manufacturing techniques such as selective laser sintering (SLS), or electron beam melting (EBM). A comparison between the old destructive testing methods and this innovative non-destructive approach underscores the possible fundamental change toward more efficient and sustainable manufacturing practices. This approach has the potential to significantly reduce the time and cost associated with traditional destructive testing methods while ensuring the quality of FFF-manufactured products.
Absorber-free laser transmission welding enables precise and clean joining of polymer foils without absorbent additives or adhesives. It is well suited for applications in medical technology and food industry, which impose high demands on process reliability. To achieve a large process window and thus a reliable process, a homogeneous weld seam temperature is desirable. For this purpose, the intensity distribution of the laser beam is adapted locally by refractive beam shaping optics. Using a donut-shaped intensity distribution, the weld seam temperature is homogenized. Thus, the process window for welding polypropylene or polyethylene foils is enlarged up to a factor of 4 compared to a conventional, Gaussian-shaped distribution. This enables the reliable welding of even 85 µm thin foils, which could only be welded to a limited extent with a conventional laser intensity distribution.
